a. Field of the Invention
The present invention generally relates to output driver circuits, and more particularly, to reducing leakage in output driver circuits.
b. Background of Invention
An associative memory system such as Content Addressable Memory (CAM) may facilitate its memory cells to be referenced by their contents. Thus, CAM may be utilized in, for example, lookup table implementations, networking system applications, pattern recognition, and data compression. Among other things, CAMs provide the ability to perform a fast search operation in which search data is compared with data stored within the CAM. Typically search data is loaded onto search lines and compared with stored words in the CAM. During a search-and-compare operation, the CAM may perform a fully parallel search and generate a match or mismatch signal associated with each stored word, indicating whether the search word matches a stored word or not.
In order to allow this fast parallel comparison between all stored words to a single search word, each CAM word may contain dedicated search hardware. Each CAM cell, therefore, contains additional bit-comparison transistors, in addition to a conventional storage element, which may typically be implemented as a Static Random Access Memory (SRAM) cell or a Dynamic Random Access Memory (DRAM) cell. This added circuitry is combined across the word with a match-line (ML) to produce a match or mismatch signal for each CAM word. Moreover, this search hardware allows the entire contents of the CAM memory to be searched in a single memory cycle.
Since, leakage power minimization is becoming increasingly important as technology nodes progress, leakage power reduction in each component on a chip may also be of significance. One major contributor to CAM leakage may be matchline output drivers, which ultimately drive the search results. For example, a Ternary CAM (TCAM) system may include 8096 matchlines and, therefore, 8096 output drivers, which may contribute to current leakage and increased power consumption. Furthermore, most of the TCAM matchlines typically drive a miss state or GND causing leakage in the PFET drivers of their output drivers.